1. Field of the Invention
The present invention relates to lumber work boats provided with an operating arm assembly for handling lumber at a bow portion of the boat. More particularly, the invention relates to a lumber work boat, in which at the bow portion there is formed a frontwardly open recess, within which the afore-mentioned operating arm assembly may be received, said operating arm assembly being driven by a drive mechanism disposed interiorly of the hull.
2. Description of the Prior Art
It is difficult to gather up or re-arrange lumber floating on the surface of the water, or to move the lumber from one position to another in a floating condition, and hence, lumber work boats are conventionally used to efficiently carry out such lumber handling operations. The lumber work boat is provided with a lumber handling device for handling lumber floating on the surface of the water, and this device may be power operated. The lumber work boat can handle the lumber efficiently, but in order to accomplish the work in more efficient and safe manner, the lumber work boat must be of the type which can turn in a small circle to allow the boat to freely and actively move in narrow waterways or between lumber, and which has high stability so that the boat may operate under stable conditions.
In the known lumber work boats, the lumber handling device is usually disposed on the upper deck of the hull of the boat. Since the lumber work boat is constructed to be as small as possible to enhance its mobility, with a heavy work device disposed on the upper deck, the center of gravity of the entire boat is raised which decreases the stability of the boat.
Usually, the work devices such as the lumber handling device are disposed at the bow portion. For this reason, the weight of the bow portion is increased to move the center of gravity of the entire boat forwardly, resulting in reduction of sea worthiness of the hull adversely affecting navigation, and difficulty in carrying out stabilized operation.
If the work device is disposed on the upper deck, the height of the work device above the water surface is great, and therefore, for example, in the case where lumber on the water surface is gathered up at the broadside of a large boat, when the lumber work boat tries to come near the stern of the large boat, the work device comes into contact with the stern portion of the large boat, as a consequence of which the lumber flowing into the narrow portion of the stern portion of the large boat cannot be gathered up and in addition, the stern portion of the large boat may be damaged.
Since a load is exerted upon the tip portion of the work device during operation, the construction of the boat where the work device is mounted must be made rigid when the latter is disposed on the upper deck. However, if the mounting portion for the work device employs a rigid construction, such portion will increase in weight because of the provision of such construction, whereby it is difficult to maintain the weight balance of the hull of the boat.
Furthermore, drive devices such as hydraulic cylinders adapted to drive the work device and precision machining members, such as bearings, used in support portions of the work device are disposed on the deck, whereby these devices and members easily rust and materially impair the durability of these devices and members. As a result, the hydraulic system is susceptible to damage and oil leaked through the damaged portions flows out onto the surface of the water to contaminate the water.